Mercruiser 5.0 MPI seized up while running

[chrisonethree]

I just purchased a 2004 Baja 202 Islander with 5.0 MerCruiser 5.0 MPI (280 hours), and had it looked over and ran by a marine surveyor who gave me the green light on the boat and said no issues.

Due to high water levels I was only able to run the boat 3 times since purchasing 2 weeks ago, on the 3rd ride the boat was running great, no overheating, no vibrations, no odd noises, etc. and while running at about 45 MPH the boat just dies on me. No sputtering, no loud noise, nothing, just straight lost power. I get towed back to the dock thinking maybe it's a bad fuel gauge, so I add some gas and try to start it and it's not starting. I can't believe it's a starter as that wouldn't have any effect on it while running. We hear the fuel pump engaging. We tried manually turning it only to find out the motor is locked up.

We're assuming possibly a bent piston maybe? What could have caused this so suddenly? Any other guesses on what could have happened?

 

[alldodge]

Start by pulling the drive. If the drive is locked up you cannot turn the motor

 

[Bondo]

Ayuh,.... Welcome Aboard,..... It sure sounds like either the motor, or the drive locked up,....

As AD says, pull the drive to see which 1,....

 

[Rick Stephens]

Pull all the plugs and make sure it isn't full of water. If you were cruising along at speed and the motor died for whatever reason, if the exhaust shutters aren't 100% the wave that runs into the stern is sure enough to fill the manifolds, and the cylinders, with water.